1. Field of the Invention
The present invention relates to liquid containers comprising a float in a liquid chamber.
2. Description of Relate Art
A known liquid container is configured to store liquid therein and to be removably mounted to a liquid-consuming apparatus. When the liquid container is mounted to the liquid-consuming apparatus, liquid stored in the liquid container is consumed by the liquid-consuming apparatus. Another liquid container is positioned in and unremovably fixed to a known liquid-consuming apparatus. In such known liquid containers, the presence/absence of liquid or the remaining amount of liquid stored in the liquid container is regarded as necessary information for a user in using the liquid-consuming apparatus. Examples of such a liquid container include an ink cartridge to be mounted to a printer when the printer is used, and an ink tank positioned in and unremovably fixed to a printer. As methods of determining the presence/absence of ink or the remaining amount of ink stored in the ink cartridge or the ink tank, a known method has been provided, in which the change in the level of ink surface is detected with a float positioned in the ink cartridge or the ink tank. For example, a known ink cartridge such as an ink cartridge described in JP-A-2008-254194, has a float supported by an arm. When a sufficient amount of ink remains in this ink cartridge, the float tends to float on the liquid surface with its buoyancy. However, because the movement of the arm is regulated, the float is submerged in the ink. When the remaining amount of ink becomes small and the liquid surface descends, a portion of the float is exposed above the liquid surface. Subsequently, following the descending liquid surface, the float moves down. A known ink tank such as an ink tank described in JP-A-63-147650 has a float always floating on the liquid surface and moves down following the descending of the liquid surface.
Bubbles or films of liquid may be generated in the above-described liquid containers. Such bubbles or films of liquid may adhere to and push up the float, or the surface tension of bubbles or films of liquid contacting the float and a wall of the liquid container may hinder the movement of the float. For these and other reasons, there has been a problem that the float may not follow the movement of the liquid surface descending along with the consumption of ink.
To solve this problem, the mass or weight of the float is increased, whereby a gravity equivalent to the increased mass or weight is added to the float. The additional gravity enables the float to break the bubbles or the films of liquid adhering to the float, such that the float can move following the descending liquid surface.
Before the ink cartridge described in JP-A-2008-254194 is used, that is, when there is a sufficient amount of ink remaining in the ink cartridge, the float is in the highest position within the movable range of the float within the ink. It is the buoyancy acting on the float that pushes up the float to the highest position. Therefore, when the mass or weight of the float is simply increased as described above, which means that the force (gravity) that moves down the float increases, the force that pushes up the float, i.e., the resultant force of the buoyancy and the gravity, is reduced.
Bubbles or films of ink may be already generated in the ink cartridge before the ink cartridge is used because of, for example, vibrations occurring during the transportation of the ink cartridge. In such a case, if the force that pushes up the float is reduced with the increase of the mass or weight of the float as described above, the force that pushes up the float cannot overcome the hindering force of the bubbles or films of ink, such that the float cannot move up to the highest position. Consequently, it may be determined that the remaining amount of ink is small, despite that the cartridge is not used.
Similarly, if the mass or weight of the float is increased in the ink tank described in JP-A-63-147650, the float may not be able to move up to the highest position because of the hindering of bubbles or the films of ink, despite that the ink tank is full of ink. Consequently, it may be determined that the remaining amount of ink is less than the full amount.